Etching a substrate: processes – Nongaseous phase etching of substrate – Using film of etchant between a stationary surface and a...
Reexamination Certificate
2000-05-04
2002-05-14
Goudreau, George (Department: 1763)
Etching a substrate: processes
Nongaseous phase etching of substrate
Using film of etchant between a stationary surface and a...
C216S089000, C216S084000, C438S692000, C438S693000, C438S005000, C438S750000, C451S041000, C451S057000, C451S060000, C451S005000, C451S036000, C451S037000
Reexamination Certificate
active
06387289
ABSTRACT:
TECHNICAL FIELD
The present invention is directed toward mechanical and/or chemical-mechanical planarization of microelectronic-device substrate assemblies. More specifically, the invention is related to planarizing machines and methods for selectively using abrasive slurries on fixed-abrasive planarizing pads.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarizing processes (collectively “CMP”) remove material from the surface of semiconductor wafers, field emission displays or other microelectronic substrates in the production of microelectronic devices and other products.
FIG. 1
schematically illustrates a CMP machine
10
with a platen
20
, a carrier assembly
30
, and a planarizing pad
40
. The CMP machine
10
may also have an under-pad
25
attached to an upper surface
22
of the platen
20
and the lower surface of the planarizing pad
40
. A drive assembly
26
rotates the platen
20
(indicated by arrow F), or it reciprocates the platen
20
back and forth (indicated by arrow G). Since the planarizing pad
40
is attached to the under-pad
25
, the planarizing pad
40
moves with the platen
20
during planarization.
The carrier assembly
30
has a head
32
to which a substrate
12
may be attached, or the substrate
12
may be attached to a resilient pad
34
in the head
32
. The head
32
may be a free-floating wafer carrier, or an actuator assembly
36
may be coupled to the head
32
to impart axial and/or rotational motion to the substrate
12
(indicated by arrows H and I, respectively).
The planarizing pad
40
and a planarizing solution
44
on the pad
40
collectively define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the substrate
12
. The planarizing pad
40
can be a fixed-abrasive planarizing pad in which abrasive particles are fixedly bonded to a suspension material. In fixed-abrasive applications, the planarizing solution
44
is typically a non-abrasive “clean solution” without abrasive particles. In other applications, the planarizing pad
40
can be a non-abrasive pad composed of a polymeric material (e.g., polyurethane), resin, felt or other suitable materials. The planarizing solutions
44
used with the non-abrasive planarizing pads are typically abrasive slurries with abrasive particles suspended in a liquid.
To planarize the substrate
12
with the CMP machine
10
, the carrier assembly
30
presses the substrate
12
face-downward against the polishing medium. More specifically, the carrier assembly
30
generally presses the substrate
12
against the planarizing liquid
44
on a planarizing surface
42
of the planarizing pad
40
, and the platen
20
and/or the carrier assembly
30
move to rub the substrate
12
against the planarizing surface
42
. As the substrate
12
rubs against the planarizing surface
42
, material is removed from the face of the substrate
12
.
CMP processes should consistently and accurately produce a uniformly planar surface on the substrate to enable precise fabrication of circuits and photo-patterns. During the construction of transistors, contacts, interconnects and other features, many substrates develop large “step heights” that create highly topographic surfaces. Such highly topographical surfaces can impair the accuracy of subsequent photolithographic procedures and other processes that are necessary for forming sub-micron features. For example, it is difficult to accurately focus photo patterns to within tolerances approaching 0.1 micron on topographic surfaces because sub-micron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes are often used to transform a topographical surface into a highly uniform, planar surface at various stages of manufacturing microelectronic devices on a substrate.
In the highly competitive semiconductor industry, it is also desirable to maximize the throughput of CMP processing by producing a planar surface on a substrate as quickly as possible. The throughput of CMP processing is function, at least in part, of the polishing rate of the substrate assembly and the ability to accurately stop CMP processing at a desired endpoint. Therefore, it is generally desirable for CMP processes to provide (a) a uniform polishing rate across the face of a substrate to enhance the planarity of the finished substrate surface, and (b) a reasonably consistent polishing rate during a planarizing cycle to enhance the accuracy of determining the endpoint of a planarizing cycle.
Although fixed-abrasive planarizing pads have several advantages compared to fixed-abrasive pads, fixed-abrasive pads may not produce consistent polishing rates throughout a planarizing cycle. One drawback of fixed-abrasive pads is that the polishing rate may be unexpectedly low at the beginning of a planarizing cycle. The inconsistency of the polishing rate for fixed-abrasive pads is not completely understood, but when a non-abrasive planarizing solution is used on a fixed-abrasive pad, the polishing rate of a topographical surface starts out low and then increases during an initial stage of a planarizing cycle. Such an increase in the polishing rate of a topographical substrate is unexpected because the polishing rate of a topographical substrate on a non-abrasive pad with an abrasive slurry generally decreases during the initial stage of a planarizing cycle. Therefore, it would be desirable to increase the consistency of the polishing rate on fixed-abrasive pads.
Another drawback of fixed-abrasive pads is that the polishing rate is low when planarizing a blanket surface (e.g., a planar surface that is not yet at the endpoint). The polishing rate of blanket surfaces is also relatively low on non-abrasive pads, but the polishing rate of such surfaces is generally even lower on fixed-abrasive pads. Therefore, it would be desirable to increase the polishing rate of blanket surfaces when using fixed-abrasive pads.
SUMMARY OF THE INVENTION
The present invention is directed toward planarizing machines and methods for selectively using abrasive slurries on fixed-abrasive planarizing pads in mechanical and/or chemical-mechanical planarization of microelectronic substrate assemblies. In one embodiment of a method in accordance with the invention, a microelectronic substrate is planarized by positioning a fixed-abrasive planarizing pad on a table of a planarizing machine, covering at least a portion of a planarizing surface on the pad with a first abrasive planarizing solution during a first stage of a planarizing cycle, and then adjusting a concentration of the abrasive particles on the planarizing surface at a second stage of the planarizing cycle. The fixed-abrasive pad can include a planarizing medium comprising a binder and a plurality of first abrasive particles fixedly attached to the binder so that at least a share of the first abrasive particles are exposed at the planarizing surface. The first abrasive planarizing solution has a plurality of second abrasive particles that are distributed across at least a portion of the planarizing surface during the first stage of the planarizing cycle. The first abrasive planarizing solution and the fixed-abrasive pad operate together to remove material from the microelectronic substrate. For example, material can be removed from the microelectronic substrate by rubbing the substrate against the first abrasive particles at the planarizing surface and the second abrasive particle suspended in the first planarizing solution.
The concentration of the second abrasive particles on the planarizing surface can be adjusted during the second stage of the planarizing cycle by a number of different procedures. In one embodiment, the planarizing surface is coated with a second non-abrasive second planarizing solution without abrasive particles during the second stage of the planarizing cycle to reduce the concentration of the second abrasive particles on the planarizing surface. The second planarizing solution can be dispensed onto the planarizing surface after termin
Goudreau George
Micro)n Technology, Inc.
Perkins Coie LLP
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